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Development of an Eye Tracker

Development of an Eye Tracker. By Jason Kajon Barrett of the Center for Imaging Science at the Rochester Institute of Technology Advisor: Jeff Pelz. What is an Eye Tracker?. A device used to detect eye motion. What are they for ? Access for the physically handicapped,

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Development of an Eye Tracker

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  1. Development of an Eye Tracker By Jason Kajon Barrett of the Center for Imaging Science at the Rochester Institute of Technology Advisor: Jeff Pelz

  2. What is an Eye Tracker? • A device used to detect eye motion. • What are they for ? • Access for the physically handicapped, • target variable resolution, • realistic virtual reality environments, • and increased bandwidth of human-computer interaction. Shannon’s Rule: C = BW log2(1 + S/N)

  3. Types of Trackers: • mechanical- corneal cover • magnetic- eyeball polarity • electric- EMG & EOG • optical- IR illumination

  4. What is the Research Design? • A device using four IR photodetectors and a microcontroller to detect the onset of rapid eye motion. A PicBasic program to run this device.

  5. Why a microcontroller ? • Simple data manipulation, • lookup table, • single upgradable chip, • cost for device, • and ease burden on CPU.

  6. Targets for the Research • < $300 Project Expense • 500 Hz Sampling Rate • < 4 Degrees Accuracy

  7. Microcontroller and instructions $ 25 Crystal $ 2 Power Supply $110 Comparator $ 7 Diff. OP-AMP $ 5 Potentiometers $ 20 IR Emitters $ 67 IR Detectors $ 45 Total $281 Initial Budget

  8. Targets for the Research • < $300 Project Expense • 500 Hz Sampling Rate • < 4 Degrees Accuracy

  9. Why 500 Hz ? • Saccades- rapid eye movements • last 30 - 120 ms, • cannot be within 100 ms of eachother • video eye tracking unit at 60 Hz (i.e. 17 ms, half a short saccade.)

  10. Sampling Rate • 200 hsec / instruction • 200 instructions • 40 msec for sample • 50 kHz sample rate For a 20 MHz PIC16C74A/JW-ND processor

  11. Sampling Rate • 20 msec / instruction • 100 instructions • 2 msec for sample • 500 Hz sample rate For a 10 MHz PIC16C84 processor

  12. Targets for the Research • < $300 Project Expense • 500 Hz Sampling Rate • < 4 Degrees Accuracy

  13. Why 4 Degrees? The fovea covers approximately a 10 Field of View. Video eye trackers can come to within 1/2 0 for field of view. The main consideration is speed.

  14. individual calibration will be necessary extensive lookup table creation consecutive ON/OFF state comparison ( provided for by software ) To get within 4 Degrees:

  15. Sample Calibration Target (with Nine Targets)

  16. Sample Calibration Target (with Seventeen Targets)

  17. The Proposed Design • ASL Model 210 Eye Movement Monitor • made from scratch • single eye measurement • fit within HMD

  18. Vertical | ? | Horizontal + _ ASL model 210 eye movement monitor

  19. Horizontal Measurement + _ • Negative measurement = left • Positive measurement = right

  20. Right Center Left Detector Positions as the Viewer Shifts Their Horizontal Gaze

  21. Vertical Measurement | ? | • High measurement = up • Low measurement = down

  22. Up Center Down Detector Positions as the Viewer Shifts Their Vertical Gaze

  23. ASL video eye tracker

  24. Long-term Goals of the Research • Measurement of saccadic eye movements. • Use in future projects involving eye contingent updating and the study of perception.

  25. Conclusions The eye tracker proposed is possible for the proposed expense as there is an adequate sacrifice for accuracy of eye position to increase the speed. The resultant code written in PicBasic will satisfy the design proposed.

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